1. Field of the Invention
The present invention relates to a method and apparatus for supplying a gas used in semiconductor processing, and more particularly, to a method and apparatus for supplying a gas into a chamber using a dispersion head.
2. Description of the Related Art
The elements of a semiconductor device are becoming more densely integrated to improve the processing speed and increase the storage capacity. However, with increases in processing speed, storage capacity, and integration density, the manufacturing techniques to produce the devices must keep pace and become increasingly sophisticated to ensure the production of proper functioning and reliable devices.
Areas of particular focus to ensure reliability and integrity during the processing sequence are chemical vapor deposition techniques for the formation of thin films, and plasma etching techniques for the forming patterns in the thin films.
As the design rule for newer semiconductor devices advances towards 0.15 xcexcm or less, it is imperative that the thin films and patterns formed on the substrate have uniform thicknesses. To ensure uniformity in the resulting films and patterns, the supply of gas used to form the films and patterns should be uniform, and thus should be continually checked and controlled.
Accordingly, the equipment used for forming a film or a pattern include an apparatus to supply the gas uniformly, such as a dispersion head and a diffuser, which is disposed in the dispersion head.
These types of equipment are disclosed in Japanese Patent Laid-Open Publication No. Hei 2-71511, Japanese Patent Laid-Open Publication No. 2000-58294, U.S. Pat. No. 5,595,602 (issued to Harlan et al.), and Korean Patent Laid-Open Publication No. 1998-82853, described later.
FIG. 1 is a simplified schematic view of a processing apparatus used in a conventional semiconductor process. Referring to FIG. 1, this processing apparatus corresponds to either a film forming apparatus for forming a film on a substrate (W), or an etching apparatus for etching a film formed on a substrate to form a pattern. The selection of whether the apparatus is a film forming apparatus or an etching apparatus is determined by the process condition.
The processing apparatus has a chamber 10, and includes therein a pedestal 101 on which the substrate (W) is mounted at a lower portion of the chamber 10, a dispersion head 103 positioned at an upper portion of the chamber 10 and confronting the substrate (W), and a diffuser 105 disposed within the dispersion head 103. The dispersion head 103 has an inlet at one side thereof, into which a source gas is introduced, and an outlet at the other side thereof through which the source gas is discharged. Thus, the gas is introduced through the inlet of the dispersion head 103 and is diffused by the diffuser 105 to be supplied, through the outlet of the dispersion head 103, onto the substrate (W) placed in the chamber 10.
FIG. 2 is a perspective view of the plate-shaped diffuser 105 disposed within the dispersion head 103 of FIG. 1. The diffuser 105 is disposed within the dispersion head 103 to block and deflect the source gas that is supplied through the dispersion head 103, thereby diffusing the gas. As a result, this diffused gas has a uniform distribution as it is supplied onto the substrate (W) placed in the chamber 10.
In addition to the aforementioned plate shape, the diffuser 105 may have various other suitable shapes, so long as the gas is diffused and supplied uniformly to the substrate (W).
For example, U.S. Pat. No. 5,595,602 discloses a porous sintered diffuser to uniformly supply a gas onto the whole surface of a substrate. Korean Patent Laid-Open Publication No. 1998-82853 discloses a diffuser having a through hole formed around its central portion to uniformly supply a gas onto the whole surface of a substrate. Japanese Patent Laid-Open Publication No. 2000-58294 discloses two diffusers each having the same diameter. The two diffusers have different shaped holes that are parallel to each other, to uniformly supply a gas onto the whole surface of a substrate.
Furthermore, Japanese Patent Laid-Open Publication No. Hei 2-71511 discloses a dispersion head having holes with different diameters to uniformly supply a gas onto the whole surface of a substrate.
In each of these references, the dispersion head and the diffuser embodiments attempt to ensure the gas is uniformly supplied onto the whole surface of a substrate.
However, for diffusers having a circular shape, it has been found that while the gas is blocked, it is not diffused sufficiently, and as a result, the gas is not uniformly supplied onto the whole surface of a substrate placed in the chamber 10. This is because the gas diffused by the circular diffuser 105 is predominantly diffused around an outer circumferential portion of the dispersion head 103.
FIG. 3 is a sectional view showing a film formed on a substrate using the processing apparatus of FIG. 1. Referring to FIG. 3, a film 32 is formed on a substrate 30. The film 32 may be made of an insulator material or a metal layer, and is selected depending on the process condition. The film 32 is formed by a reaction between process gases as supplied through the dispersion head and diffuser. Ideally, if the process gases are uniformly supplied onto the whole surface of the substrate 30, the film 32 should have a uniform thickness.
However, when forming the film 32 using the apparatus of FIG. 1, a thickness l1 formed at an outer circumferential portion of the substrate 30 is greater than a thickness l2 formed at a central portion of the substrate 30. This is because the process gases are not uniformly supplied onto the whole surface of the substrate 30. More specifically, this is because the outer circumferential portion of the substrate 30 is supplied with larger amounts of the process gas larger relative to the central portion of the substrate 30.
The non-uniformity in the thickness of the film is due to the non-uniformity in the distribution of the process gases supplied, which is a primary cause of failures while fabricating semiconductor devices, thereby decreasing productivity and reliability. This non-uniform distribution of the process gases is apparently due to the structure of the dispersion head and the diffuser.
Accordingly, it is an object of the present invention to provide a method for supplying and uniformly diffusing a process gas onto the entire region of a work piece such as a wafer, including the central portion and the peripheral portion thereof.
It is another object of the present invention to provide an apparatus for supplying and uniformly diffusing a process gas onto the entire region of a work piece such as a wafer, including the central portion and the peripheral portion thereof.
To achieve the above objects and other advantages, there is provided a method for supplying a gas used in a semiconductor process, including flowing a gas in a flow direction toward a first diffuser arranged in a dispersion head. The gas is diffused a first time within the dispersion head by dispersing the gas along side directions different than the flow direction by contacting the gas and the first diffuser. A portion of the first diffused gas is guided through an outlet of the dispersion head and toward a work piece arranged in a chamber. Then, a remaining portion of the first diffused gas is diffused again by contacting the first diffused gas with a second diffuser disposed between the first diffuser and the work piece, by dispersing the gas along side directions different than the flow direction. A portion of the twice diffused gas is guided through the outlet of the dispersion head and toward the work piece arranged in the chamber.
Additional diffusers could be added within the dispersion head, and in such cases, a remaining portion of the (nxe2x88x921)-th diffused gas is diffused an n-th time by contacting the gas with an n-th diffuser disposed between the (nxe2x88x921)-th diffuser and the work piece, by dispersing the gas along side directions different than the flow direction. A portion of the n-th diffused gas is then guided through the outlet of the dispersion head and toward the work piece arranged in the chamber. In this case, n is a natural number greater than 2.
The gas is thus diffused at least twice prior to being supplied into the chamber to ensure it has a uniform distribution as supplied onto the substrate.
According to another aspect of the present invention, there is provided an apparatus for supplying a gas used in a semiconductor process, including a dispersion head having a gas supply inlet and a gas discharge outlet. A first diffuser is arranged in an upper central portion of the dispersion head, and downstream of the gas supply inlet, and a second diffuser is arranged downstream of the first diffuser and disposed radially outward of the first diffuser and toward a peripheral portion of the dispersion head. The first diffuser and second diffuser are spaced apart vertically relative to a flow direction of a gas supplied through the gas supply inlet, and spaced apart radially relative to the central and peripheral portions of the dispersion head.
Additional diffusers can be provided in the dispersion head. If so, then the n-th diffuser is arranged downstream of the (nxe2x88x921)-th diffuser and disposed radially outward of the (nxe2x88x921)-th diffuser and toward the peripheral portion of the dispersion head. The (nxe2x88x921)-th diffuser and n-th diffuser are spaced apart vertically relative to a flow direction of a gas supplied through the gas supply inlet, and spaced apart radially relative to the peripheral portions of the dispersion head. In this case, n is a natural number greater than 2.
Preferably, the first diffuser has a circular plate shape and the second diffuser has an annular plate (or ring) shape. The inner diameter of the second diffuser is greater than an outer diameter of the first diffuser. If a third diffuser is added, the inner diameter of the third diffuser is greater than the outer diameter of the second diffuser, and so on.
Preferably, the chamber is a processing chamber for forming a film using a plasma reaction, or a processing chamber for etching a film formed on the substrate using a plasma reaction. An election of such processing chambers depends on the processing conditions and desired result.
Thus, the gas is uniformly diffused at least twice prior to being supplied into the chamber and thereby it has a uniform distribution as supplied onto the substrate. As a result, it becomes possible to form a film or a pattern having a uniform thickness.